1. Field of Invention
The present invention relates generally to medical infusion devices of improved construction and performance, for use in withdrawing fluids from as well as infusing fluids into an intravenous fluid stream flowing into the circulatory system of a patient, and more particularly to drug delivery systems employing the same.
2. Brief Description Of the Prior Art
In the field of modern medicine, health care practitioners utilize various types of drug delivery systems in order to safely administer medications to patients. One such drug delivery system is an IV administration system which includes a catheter, insertable to the vein of a patient, and a source of intravenous fluid connected to the catheter by way of an IV administration set with a section of flexible medical tubing. The source of intravenous fluid is typically contained within a flexible prepackaged bag suspended from a support stand positioned above the heart of the patient. The fluid is typically fed into the first primary port of the medical infusion device by way of a drip-type connector having a drip chamber and a length of plastic tubing with one-way valve. The intravenous fluid flows from the bag through the IV set and medical infusion device, along the flexible medical tubing section and into the catheter, where the intravenous fluid enters the blood stream of the patient.
In general, each prior art medical infusion device has a main housing portion with primary inlet and outlet ports, and a fluid flow passageway disposed therebetween. The function of the primary inlet and outlet ports is to permit in-line interconnection of the device within the intravenous delivery stream. The connection may be between two sections of medical tubing, between the drip-type connector and a section of medical tubing, or between the catheter and a section of medical tubing. Such connection arrangements vary depending on site of use, and patient needs.
In order that a liquid medicine may be infused into the intravenous stream and diffused therewith prior to entering the catheterized vein of the patient, prior art medical infusion devices are provided with one or more infusion ports. The actual geometrical arrangement of the infusion ports and the primary inlet and outlet ports vary from design to design. For example, see U.S. Pat. Nos. 4,666,429 (Stone); 4,908,018 (Thomsen) and 4,915,687 (Sirerr). In general, each infusion port includes a tubular section that extends from the main housing of the medical infusion device. Within the tubular section of each infusion port, there exists a check valve opening and check valve element, oftentimes realized as a resilient disc.
In a one-way check valve design, the check valve element is arranged in a normally closed configuration along its associated infusion tube. When a supply of liquid medication is injected into the infusion port by either a needleless injection syringe or medical tube delivery arrangement, a pressure-differential is created across the check valve by the incident fluid medication, causing the check valve element to reconfigure into its open configuration and thus permitting the liquid medication to flow through the check valve opening, into the intravenous stream passing through the housing of the medical infusion device, and ultimately into the circulatory system of the catheterized patient. Examples of prior art one-way check valve designs that have been connected to medical infusion devices are disclosed in U.S. Pat. No. 4,535,820.
In a two-way check valve design, a check valve is attached that permits injection and/or aspiration. Normally, the check valve is arranged in a closed configuration, preventing fluid medication to flow across the check valve opening and into the intravenous stream. When a check valve plunger is physically actuated (i.e., displaced) towards a check valve opening, the check valve element is rearranged and held in an open configuration, permitting gravity flow or two-way fluid flow across the check valve opening. The advantage of such medical infusion devices is that they can be used to inject or drip fluid medications into the primary fluid stream as well as aspirate fluids therefrom as desired or required in various patient applications. Examples of two-way check valve designs are disclosed in U.S. Pat. Nos. 4,683,916 and 5,190,067.
While most prior art medical infusion devices of the designs described above have proven useful to the medical arts, such devices have not been without significant shortcomings and drawbacks.
In particular, prior art medical infusion devices have check valve structures mounted along the tubular sections of their infusion ports. Thus, it has not been possible to infuse medications and nutrients directly into the primary intravenous stream flowing through such prior art medical infusion devices. This has resulted in a number of significant consequences. In particular, when using a needleless injection syringe to inject a dosage of medication into the infusion port of a prior art medical infusion device, a residual amount of such injected medication unavoidably resides (i.e., accumulates) along the infusion tube portions of prior art medical infusion devices, (i.e., between the check valve opening and the device housing) and never infuses into the intravenous stream. Thus, when using prior art medical infusion devices, it has been very difficult to determine whether a precisely metered dosage of injected medication is actually infused into the patient's circulatory system.
The placement of check valve structures along the infusion tube portions of prior art medical infusion devices necessitates that such infusion tubes be longer than otherwise desired. Consequently, the infusion tube portions of prior art medical infusion devices have been susceptible to fracture when connecting infusion devices to the infusion ports, due primarily to torques generated therealong during fluid infusion and aspiration operations.
Prior art medical infusion devices require the use of solvent bonding in order to securely bond check valve structures to their respective infusion ports. Consequently, this feature of prior art medical infusion devices has resulted in the undesirable leaking and cracking of check valves and the medical infusion devices within which they are installed.
The use of sonic welding or solvent bonding to connect discrete infusion tubes to the housing of prior art medical infusion devices has resulted in devices susceptible to fracture and thus fluid leakage.
In addition, the overall design and construction of prior art medical infusion devices have rendered manufacturing such devices a complicated process, thus increasing the overall cost of such medical devices.
Thus, there is a great need in the art for a medical infusion device of improved design and construction which can be used to inject as well as aspirate fluids passing through its primary fluid flow channel, while avoiding the shortcomings and drawbacks of prior art device and methodologies.